Timing device



Nov. 2, 1954 Filed Aug. 22, 1952 P. H. MORGANSON TIMING DEVICE 3 Sheets-Sheet l Nov. 2, 1954 P. H. MORGANSON TIMING DEVICE Filed Aug. 22, 1952 5 Sheets-Sheet 2 V five/7501': Pete]- Hf/azywvson 1954 P. H. MORGANSON 2,693,231

TIMING DEVICE Filed Aug. 22, 1952 3 Sheets-Sheet 3 United States Patent TIMING DEVICE Peter H. Morganson, Winsted, Conn., assignor to The William L. GilbertClock Corporation, Winsted, Conn., .a corporation ofConnecticut Application August 22, 1952, Serial No. 305,751

Claims. (Cl. 161-1) This invention relates to timing devices in general, and to timing devices for performing identical timecycles in particular.

The timing device to which the present invention relates is suited for operating electric circuits or various apparatus for equal predetermined time periods.

The timing principle underlying the present timing device is the same as that of the previous timer shown and described in my copending application Serial No. 300,665, filed July 24, 1952. This previous timer has a timing member in the form of a pivoted arm which is spring-urged into a home position, and which may .be turned into any one of an infinite number of operative positions for starting a time-cycle performance of any desired duration. The cycle is determined by the time required for the spring-return of the timing member from operative to home position under the control of a fluid-friction brake having a brake rotor which is operatively connected with the timing member and exerts a uniform'brake force on the latter to prevent uncontrolled run-away of the same under the compulsion. of its driving spring and, instead, compel it to escape into home position at a uniform controlled speed. Interposed between the brake rotor and timing member is a reduction drive which compels the timing membet to turn at a speed that is considerably slower than that of the brake rotor, so that the torque imparted to the timing member by its driving spring may be quite considerable for operating without fail an electric switch or any other control device at the end of a timecycle, and the brake force on the rotor may nevertheless -be comparatively small for assuredly holding the timing member against uncontrolled escape under the compulsion of its driving spring. Included in this reduction drive is a friction coupling so that the timing member may quickly be shifted into an operative position without appreciable resistance from the fluid-friction brake. More -particularly,,the reduction drive is a train of gears of which the slow gear will be meshed with a gear segment on the timing member on turning the latter into an operative position,'and will be demeshed from this gear segment after an initial part of the return :motion of the timing member into home position, so that the latter is thereafter forced through the remainder of its return motion into home position by the quick action and full force of its driving spring. It isduring this remainder of the unimpeded return motion of the timing member into home position that the same will quickly and forcefully operate an electric switch or other control device.

It is an object of the present invention to provide a timing device of .a type which operates on the timing principle of my above-mentioned prior timer, and which will perform equal pre-determined time cycles that-may conveniently be initiated or started electrically by local or remote control, as desired.

It is another object of the present invention to provide a timing device of this type of which the timing member is shifted into its operative position by a momentarily energized solenoid.

A further object of the present invention is to provide a timing device of this type of which the timing member is shifted into its operative position either by a straight-motion plunger-type solenoid or a solenoid of the rotary armature type.

Another object of the present invention is to provide a timing device of this type in which a one-way 2,693,231 Patented Nov. 2, 1954 clutch is interposed in the drive between the brake rotor and timing member to permit the easy and quick shift of the latter into its operative position by a solenoid without any resistance whatsoever from the fluidfriction brake, and provisions are made for holding the part of the drive from the driving member of the oneway clutch to the slow gear against creepage, especially in the direction unimpeded by the clutch, at all times except when the gear segment on the timing member is in mesh with the slow gear of the drive, so that the slow gear will always be in position for ready and unfailing mesh of its teeth with those of the gear segment on the timing member when the latter is quickly shifted into its operative position for a time-cycle performance of the device.

It is a further object of the present invention to provide a timing device of this type of which the gear se ,ment on the timing member is provided with a pointed tooth which toward the end of the return motion of the timing member into home position will move radially against the slow gear of the drive and unfailingly enter the gap between two successive teeth thereof, thereby locking the slow gear in an angular position in which the teeth of the segment will never jam with those of the slow gear but will readily mesh therewith on each quick shift of the timing member into its operative position, even if the slow gear should for any reason have turned to any extent after the last release of the gear segment therefrom and prior to its last interlock with the pointed tooth on the gear segment.

It is also among the objects of the present invention to provide a timing device of this type which is exceedingly simple in construction, yet highly reliable and accurate in performance, and which may be formed in a self-contained unit of little bulk and readily lends itself to efiicient mass production at low cost.

Further objects and advantages will appear to those skilled in the art from the following, considered in conjunction with the accompanying drawings.

In the accompaying drawings, in which certain modes of carrylng out the present invention are shown for illustrative purposes:

Fig. 1 is a plan view of a timing device embodying the present invention;

Fig. 2 is a section through the device taken on the line 2-2 of Fig. 1;

Fig. 3 is a side elevation of the device as viewed in the direction of the arrow 3 in Fig. 1;

Fig. 4 is a view similar to Fig. l, but showing the device in a different operating condition;

Fig. 5 is an enlarged fragmentary section through the device, taken substantially on the line 55 of Fig. 1;

Fig. 6 is a plan view, partly in section, of a timing device embodying the present invention in a modified manner; and

Fig. 7 is a section taken substantially on the line 77 of Fig. 6.

Referring to the drawings, and more particularly to Figs. 1 to 3 thereof, the reference numeral 10 designates a timing device the operating parts of which are carried by a base or mounting plate 12, and in part also by another mounting plate 14 which is held in spaced parallel relation with the base plate 12 by a plurality of interposed pillars 16. Among the operating parts of the device is a timing member 18, currently in the form of two spaced arms 20 and 22 and a crossbar 24 of which the arms 20 and 22 may suitably be carried by a rotary sleeve 26 on a staff 28 that is journalled with its opposite ends in the mounting plates 12 and 14 (see also Fig. 5). Also mounted on the sleeve 26, and hence rotatable with the timing member 18, is a gear segment 30 which is adapted to be meshed with a pinion 32. The pinion 32 is in this instance fast on a reduced portion 34 of a collar 36 which is freely rotatable on a staff 38 that is suitably journalled with its opposite ends in the mounting plates 12 and 14 (Fig. 5). Drivingly connected with the pinion 32, through a one-way clutch 40 to be described, is a larger gear 42 which is in permanent mesh with a pinion 44 on the drive shaft 46 of a fluidfriction brake 48 on the mounting plate 12. It appears from Figs. 1 and 5 that the pinions 32 and 44 and the 3 gear 42 form a reduction gearing 50 of which the drive shaft 46 of the fluid-friction brake 48 is the fast shaft and the staff 38 is the slow shaft.

The timing member 18 is normally yieldingly urged into the home or time-cycle finish position shown in Fig. 1 by means of a torsion spring 52 which surrounds the sleeve 26 and has its ends 54 and 56 anchored to the gear segment 30 and the mounting plate 14, respectively, in the manner shown in Figs. 1 and 3. The spring 52 is preferably preloaded so as to retain the timing member 18 with some force in the home position shown in Fig. 1 in which the gear segment 30 bears against a stop pin 58 on the mounting plate 14.

The timing member 18 is, in the present example, adapted to actuate an electric switch 60 at the end of each timing cycle of the device. To initiate a timing cycle, the timing member 18 is swung from its home position (Fig. 1) into an operative or time-cycle starting position (Fig. 4), in the course of which the gear segment 30 on the timing member 18 is brought into mesh with the pinion 32 of the reduction gearing 50. On shifting the timing member 18 with its gear segment 30 into operative position (Fig. 4) and then releasing the same, the driving spring 52 will tend to return these parts quickly into home position. However, the fluidfriction brake 48 will, through intermediation of the reduction gearing 50 and one-way clutch 40, control the escape of the timing member 18 toward home position so that the same will have a slow and uniform escape motion while the gear segment 30 is in mesh with the pinion 32. As soon as the gear segment 30 moves out of mesh with the pinion 32, the former is free to turn quickly through the remainder of its return motion into home position under the full force of the spring 52 and unimpeded by the fluid-friction brake 48. It is during this unimpeded and greatly accelerated part of the return motion of the gear segment 30 into home position that the timing member 18 actuates the switch 60 force fully and in quick and accurately timed fashion.

The beforementioned one-way clutch 40 comprises a driving member 66 and a driven companion member 68 (Figs. 1 and of which the driving member 66 is in this instance a clutch spring and the driven member 68 is a clutch disc. The clutch disc 68 has a hub 70 which is suitably secured, as by pin 72, to the staff 38. Suitably mounted at 74 on the hub 70 of the clutch disc 68 is the previously mentioned gear 42. The clutch spring 66, one end of which is anchored at 76 on the collar 36, extends substantially tangentially from this collar and has its outer end 78 bent against, and preferably looped around, the periphery of the clutch disc 68. The spring 66 is preferably somewhat flexed so that its end 78 will engage the periphery of the clutch disc 68 with a slight yielding force.

The action of this conventional type of one-way clutch 40 is as follows. Thus, on turning the pinion 32 counterclockwise as viewed in Fig. 1, the end 78 of the spring 66 will slide idly on the periphery of the clutch disc 68 and fail to impart any rotary. motion to the same, especially since rotation of the clutch disc is resisted by the fluid-friction brake 48 with which it is drivingly connected by the gear 42 and pinion 44. Accordingly, the fluid friction brake 48 will not in any way impede the shift of the timing member 18 from home position into operative position, in the course of which the pinion 32 and clutch spring 66 are turned in counterclockwise direction (Fig. 1). However, the gear segment 30 will, during part of the return motion of the timing member 18 from operative to home position, turn the pinion 32 in clockwise direction as viewed in Fig. 4, causing thereby the end 78 of the clutch spring 66 to grip the pe- 'riphery of the clutch disc 68 with sufficient force to compel the latter to follow the clutch spring 66 and the pinion 32 and thus establish a driving connection between the fluid-friction brake 48 and the timing member 18 through the reduction gearing 50. Accordingly, the one-way clutch 40 will be disengaged during each shift of the timing member 18 from home position into operative position, and will be engaged during a part of each return motion of the timing member 18 into its home position. In having the one-way clutch 40 engaged during a part of each return or cycle motion of the timing member 18, as described, the escape of the latter from operative position toward home position is under the control of the fluid-friction brake 48 while the gear segment The actuator arm 122 extends in slot 134 in the arcuate wall 132 of the keeper 130 (Figs.

30 is in mesh with the pinion 32. The action of the fluid-friction brake 48 to be described is such as to prevent uncontrolled run-away of the timing member 18 under the compulsion of its driving spring 52, and instead compel the timing member to escape at a relatively slow and uniform speed while the gear segment 30 is in mesh with the pinion 32.

The fluid-friction brake 48 (Fig. 5) comprises a stator housing 80 which has a cylindrical wall 82, a top wall 84, and an outwardly extending bottom flange 86 which may be bolted or otherwise secured to the mounting plate 12. Preferably interposed between the bottom flange 86 of the stator housing 80 and the mounting plate 12 is a sealing gasket 88. Provided in the top wall 84 of the stator housing 80 and in a boss 90 therein is a bearing aperture 92 in which is journalled the previously mentioned shaft 46 that carries the pinion 44. The shaft 46 also carries a rotor 94 internally of the stator housing 80. The interior of the stator housing 80 further holds a suitable liquid 1, such as oil, for instance, which preferably has a fairly high viscosity. The rotor 94 has a cylindrical periphery 96 which is uniformly spaced from the adjacent, inner cylindrical wall surface of the stator housing 80 so as to provide therebetween a relatively narrow and uniform annular gap 3 in which the liquid 1 forms a relatively thin film f. The rotor 94 preferably has at its top and bottom some clearance from the top wall 84 of the stator housing and the mounting plate 12 so as to provide in the stator housing a reservoir 08 for a substantial supply of liquid 1. The gap g between the periphery of the rotor 94 and the inner cylindrical wall surface of the stator housing 80 is so narrow that the liquid film f therein is subjected to shearing stresses when the rotor is turned relative to the stator housing. These shear stresses are such that they exert on the rotor 94 a considerable braking force which in any event is sufiicient to hold the timing member 18 against uncontrolled run-away from operative position toward home position under the compulsion of its driving spring 52 while the gear segment 30 is in mesh with the pinion 32.

The timing device described so far in detail is, with the exception of the one-way clutch 40, similar to the timer shown and described in my aforementioned copending application Serial No. 300,665.

In accordance with one aspect of the present invention, recourse is had to a solenoid 100 for shifting the timing member'18 from home position into operative position for initiating a time-cycle performance of the device. The solenoid 100 is, in this instance, of a rotary type, and comprises a winding 102, a field 104 and an armature in the form of a permanent-magnet rotor 1 06. The field 104 is preferably formed of superposed laminations of general U-shape (Figs. 1 and 2) which are carried by pillars 108, and 112 in spaced parallel relation with the mounting plate 12. Surrounding one of the legs of the field 104 is the winding 102. The field 104 has spaced poles 114 and 116 which, on energization of the winding 102, may have the polarities or signs indicated in Figs. 1 and 4. The armature 106 is suitably carried by a staff 118 which is suitably journalled with its ends in the mounting plate 12 and an anchor plate 120 that is carried by the pillars 110 and 112 (Figs. 1 and 2). The armature 106 is, as above-mentioned, a permanent-magnet rotor which may have two pairs of poles of the signs indicated in Figs. 1 and 4. Also carried by the staff 118 is an actuator arm 122 which is adapted to cooperate with a lug 124 on an arm 126 on the sleeve 26 to shift the timing member 18 from home position into operative position when the solenoid winding 102 is energized. Mounted at 128 on the base plate 12 is a keeper 130 having an upright arcuate wall 132 which part-way surrounds the periphery of the armature 106 and is adapted to preserve its permanent magnetism. this instance through a 2 and 3), and the armature 106 is normally urged by a torsion spring 136 into the home position shown in Fig. 1 in which the actuator arm 122 rests against the adjacent end 138 of the slot 134 in the keeper (see also Fig. 3). In the present instance, the spring 136 surrounds the staff 118 and is anchored with its ends 140 and 142-to the armature 106 and the base plate 12, respectively. t

The poles of the armature 106 are, in the home position of the latter, spaced from the poles 114 and 116 of the non-energized field 104 to the extent shown in Fig. 1, and the field poles 114 and 116 of opposite signs will, on energization of the winding 102, attract the nearest poles of dissimilar signs of the armature 106 and compel the latter to turn counter-clockwise from its home position (Fig. 1) into the operative position shown in Fig. 4. It is during this partial turn of the armature 106 that the actuator arm will engage the lug 124 on the arm 126, and through the latter turn or shift the timing member 18 with its gear segment 30 from home position (Fig. 1) into operative or cycle-starting position (Fig. 4). As previously mentioned, the one-way clutch 40 will be disengaged during the shift of the timing member 18 into operative position so that the fluid-friction brake will in nowise impede this motion of the timing member under the compulsion of the solenoid 100. The shift action of the solenoid 100 on the timing member 18 and its gear segment 30 is almost instantaneous despite the resistance offered by the driving spring 52, so that momentary energization of the winding 102 is sufiicient to bring about the desired initiation of a timing cycle. Immediately on deenergization of the winding 102, the armature 106 will quickly be spring-returned to its home position (Fig. l), and the driving spring 52 will immediately compel the timing member 18 and its gear segment 30 into return motion from operative position (Fig. 4) into home position (Fig. l), partway under the control of the fluidfriction brake 48 as previously described. As also described heretofore, it is after the gear segment 30 has moved out of mesh with the pinion 32 and while it is quickly forced through the latter part of its return motion into home position under the full force of its driving spring 52 and without any further impediment from the fluidfriction brake 48, that the timing member 18 operates the switch 60. Accordingly, the duration of a timing cycle is equivalent to the time elapsing from the start of the return motion of the timing member 18 from operative position to the actuation by the latter of the switch 60 shortly before the timing member reaches its home position. All successive time-cycles of the instant device are of the same duration because the solenoid 100 will shift the timing member 18 through the same angular range on each energization of the winding 102. The time cycles of the instant device may be even more sharply defined by using the other end of the slot 134 in the keeper 130 as a stop which the actuator arm 122 may engage while the active poles of the armature 106 are still slightly out of registry with the field poles 114 and 116 of the solenoid.

The exemplary switch 60 is of the double-pole doublethrow type used, for instance, in telephone communication systems in aircraft between personnel thereof. Thus, one communication circuit may be closed via the contacts 150 and 152 on the switch blades 154 and 156, respec- Y tively, when the timing device is inoperative. However, this communication circuit is temporarily opened and another communication circuit temporarily closed for the duration of a time-cycle of the instant device when the latter is rendered operative on momentary energization of the solenoid winding 102. This other communication circuit is closed via the contacts 158 and 160 on the switch blades 156 and 162, respectively (Fig. 4). In the present instance, there are provided duplicate switches 60 on a common switch block 164 for two pairs of communication circuits (Fig. 2), and these duplicate switches will be simultaneously actuated by the timing member 18.

In accordance with another aspect of the present invention, provisions are made to prevent jamming or violent clashing of the teeth 166 of the gear segment 30 with the teeth 168 of the pinion 32, and instead assure smooth mesh of the gear segment with this pinion every time the former is shifted into the operative position shown in Fig. 4 by the action of the solenoid 100. To this end, the gear segment 30 is at the end remote from its teeth 166 provided with a finger 170 (Figs. 1 and 4) which is so arranged that the same will, toward the end of the return motion of the gear segment into home position, freely enter the ap between two successive teeth 168 of the pinion 32 when the latter is in the same angular position which it assumed at the moment of clemesh from the gear segment 30. The pinion 32 will, immediately on demesh from the gear segment 30, be ordinarily stopped by the fluid-friction brake 48 from further clockwise rotation (Fig. 1), so that the released pinion will at that time assume an angular position in which it will readily re-mesh with the gear segment. However, the released pinion 32 could turn more or less freely in the opposite direction out of its angular position of readyre-mesh with the gear segment 30, especially under vibrational or other disturbing influences to which the timing device may be subjected, were it not for the fact that the finger 170 moves into interlock with the pinion 32 so soon after demesh from the gear segment that even'disturbing influences in the meanwhile will hardly succeed in dislodging the pinion 32 from its position of ready re-mesh with the gear segment. Similarly, the action of the solenoid in shifting the gear segment 30 into operative position is so quick that even disturbing infinences will fail to dislodge the pinion 32 from its angular position of ready re-mesh for the brief instant during which the finger retracts from the pinion 32 and the teeth 166 of the gear segment move into mesh therewith. The finger 170 is relatively pointed so that it may readily force its way into the gap between the nearest successive teeth 168 of the pinion 32 and restore the latter to an accurate angular position of re-mesh with the gear segment 30 if the pinion should for any reason have crept from its normal positionof ready re-mesh after its last demesh from the gear segment and before the finger 170 reaches the pinion.

The instant timing device has all the advantages of my prior timer described in the aforementioned copending application Serial No. 300,665. Further to these advantages, the present timing device is significant for its solenoid operation in conjunction with the one-way clutch in the driving connection between the timing member and the brake rotor, permitting quick initiation of a timing cycle of the device, ready remote control over the .action of the solenoid, and also bringing about time-cycles of the same duration. Of further considerable advantage is the provision of the finger 170 on the gear segment 30 which will prevent jamming or violent clashing of the latter with the pinion 32, and instead assure their smooth re-mesh on each energization of the solenoid winding 102 and under all conditions of disturbance to which the device may be subjected.

Reference is now had to Figs. 6 and 7 which show a modified timing device 10' that differs from the described timing device 10 primarily by employing a solenoid 100' having a straight-motion push-type plunger 180. The plunger will, on energization of the solenoid winding 102, be advanced from the normal retracted position shown in Fig. 6 to engage a depending lug 182 on the pivoted gear segment 30 and shift the latter from the illustrated home position into an operative position (not shown) for starting a time-cycle performance of the device. The gear segment 30 will, during its shift into operative position, move into mesh with a pinion 32' which is operatively connected with a larger gear 42 through intermediation of a one-way clutch (not shown) which, in the present instance, is located beneath and, hence, hidden by the gear 42 in Fig. 6. This one-way clutch may be like or similar to the previously described clutch 40. The gear 42 is in permanent mesh with a pinion 44' on the rotor shaft 46' of a fluid-friction brake 48'. The one-way clutch of the instant modified timing device is so arranged that the same will be disengaged when the gear segment 30 is shifted from home position into operative position, and will be engaged when the gear segment 30' is, under the compulsion of its driving spring 52', returned to home position and while the teeth of the gear segment are in mesh with the pinion 32'. Accordingly, the action of the fluid-friction brake 48' on the gear segment 30 is the same as that of the fluid-friction brake 48 in the earlier described timing device 10, i. e., the fluid-friction brake will not impede the shift of the gear segment 30 into its operative position, but will impede and control the spring-compelled return-motion of the gear segment into home position while the gear segment is in mesh with the pinion 32. The gear segment 30 of this modified timing device is in this instance also the timing member, the side edge 186 of the same being adapted to turn a pivoted rocker 188 for actuation of a switch 60 shortly before the gear segment 30' reaches home position. The gear segment 30' is also provided with a finger 170' which performs the same function as the corresponding finger 170 in the earlier described timing device 10.

The invention may be carried out in other specific ways than those herein set forth without departing from the spirit and essential characteristics of the invention, and the present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.

This is what is claimed:

1. A timing device, comprising a pivoted timing member having a gear segment; power means normally yieldingly urging said member into a home position; a fluidfriction brake having a brake rotor; a gear train of which one end gear is drivingly connected with said rotor and the other end gear will be meshed with said gear segment on turning said member from said home position into another time-cycle starting position from which said member will, when released, escape into said home position, part-way under the control of said brake while said gear segment is in mesh with said other end gear, said gear train including a one-way clutch engaged only when said member turns into said home position; means for turning said member into said other position; and other means operative when said member is in its home position to prevent rotation of said other end gear in the direction in which it will be turned by said gear segment on turning said member into said other position.

2. A timing device as set forth in claim 1, in which said other means is operative to prevent rotation of said other end gear in either direction when said member is in its home position.

3. A timing device as set forth in claim 1, in which said gear train is a reduction gearing of which said other end gear is the slow gear.

4. A timing device, comprising a pivoted timing member having a gear segment; power means normally urging said member into a home position; a fluid-friction brake having a brake rotor; a gear train of which one end gear is drivingly connected with said rotor and the other end gear will be meshed with said gear segment on turning said member from said home position into another time-cycle starting position from which said member will, when released, escape into said home position, part-way under the control of said brake while said gear segment is in mesh with said other end gear, said gear train including a one-way clutch engaged only when said member turns into said home position; means for turning said member into said other position; and an element on said gear segment adapted, substantially on arrival of said member in its home position, to engage said other end gear and prevent rotation thereof in the direction in which it will be turned by said gear segment on turning said member into said other position.

5. A timing device as set forth in claim 4, in which said element is adapted to engage said other end gear and prevent rotation thereof in either direction substantially on arrival of said member in its home position.

6. A timing device as set forth in claim 4, in which said turning means is a solenoid having a winding and a movable part adapted on energization of said winding to engage and turn said member from said home position into said other position. I

7. A timing device, comprising a pivoted timing member having a gear segment; a spring normally urging said member into a home position; a fluid-friction brake having a brake rotor; a gear train of which one end gear is drivingly connected with said rotor and the other end gear will be meshed with said gear segment on turning said member from said home position into another timecycle starting position from which said member will, when released, escape into said home position, part-way under the control of said brake while said gear segment is in mesh with said other end gear, said gear train including a one-way clutch engaged only when said member turns into said home position; means for turning said member into said other position; and a finger on said gear segment adapted, during the latter part of each spring-return of said member into home position and while said gear segment is out of mesh with said other end gear, to enter the gap between two successive teeth of said other end gear and hold the latter in position for ready re-mesh with said gear segment on turning said member into said other position.

8. A timing device as set forth in claim 7, in which said finger is arranged on said gear segment to move substantially radially of said other end gear into and from interlocking relation with successive teeth thereof.

9. A timing device as set forth in claim 7, in which said finger is sufliciently pointed to wedge into the gap between the nearest successive teeth of said other end gear if the latter should turn after demesh from said gear segment.

10. In a timing device, the combination of a pivoted timing member having a gear segment; power means normally yieldingly urging said member into a home position; a fluid-friction brake having a brake rotor; a driving connection between said brake rotor and gear segment, said driving connection including a one-way clutch having driving and driven parts which are drivingly engaged only when said driving part is driven in one direction on rotation of said member into said home position, and a rotary gear element which will be meshed with said gear segment on turning said member from said home position into another time-cycle starting position from which said member will, when released, escape into said home position, part-way under the control of said brake while said gear segment is in mesh with said gear element; and means operative only when said gear segment is out of mesh with said gear element to orient the latter in an angular position in which said gear segment will readily remesh therewith.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 967,304 Bailey Aug. 16, 1910 1,749,185 Hicks Mar. 4, 1930 1,802,367 Bartusch et al. Apr. 28, 1931 2,106,042 Stark Jan. 18, 1938 2,234,437 Kistler Mar. 11, 1941 2,604,163 Exline July 22, 1952 

